Check for a vacuum leak around the upper intake manifold, very common for these to leak, 99 through 05 GEN III truck engines may experience any of the following:
A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle. The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. If leaking intake gasket seals are found, replace the intake gaskets. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair. The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced.
Wednesday, December 30th, 2009 AT 2:08 PM